The present invention relates to a method of operating an exhaust emission control device, and to a corresponding exhaust emission control device.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
An exhaust emission control device finds application, for example, in a drive device, especially of a motor vehicle. The drive device has an exhaust-producing device, e.g. an internal combustion engine. Emission produced during operation of the drive device is emitted, normally to the outside environment of the drive device. The exhaust emission control device is hereby used to receive and purge exhaust gas from the exhaust-producing device before being released into the surrounding atmosphere.
An exhaust emission control device includes a particulate filter by which particles contained in the exhaust are filtered out. This means, particles, e.g. soot particles or the like, collect in the particulate filter. When the load of the particulate filter with the particles reaches a limit, a regeneration mode is initiated by which the temperature of the particulate filter is increased sufficient to burn the particles or soot particles. While the regeneration mode causes a burning of the particles, there is still the problem that ash which has been produced during burning, still remains in the particulate filter. This ash cannot be carried away from the particulate filter during operation of the exhaust emission control device and/or during the regeneration mode.
The particulate filter, in particular the fill level of the particulate filter, is typically monitored by pressure sensors which determine the actual pressure loss across the particulate filter. For example, a first pressure sensor is arranged upstream of the particulate filter and a second pressure sensor is arranged downstream of the particulate filter to measure the respective actual pressures from which the actual pressure loss is computed, and based on the computed actual pressure loss, conclusion is supposed to be derived about the state of the particulate filter. This, however, is not reliable.
It would therefore be desirable and advantageous to provide an improved method of operating an exhaust emission control device to obviate prior art shortcomings and in particular to enable a reliable diagnosis about the condition of the particulate filter.